1. Field of the Invention
The present invention relates to a semiconductor device of the type which comprises a semiconductor chip attached to a substrate by anisotropic conductive adhesive. The present invention also relates to a method of making such a semiconductor device.
2. Description of the Related Art
FIG. 8 of the accompanying drawings shows an example of conventional semiconductor device, which is generally represented by reference sign 1A. The conventional device 1A includes an insulating substrate 2A and a semiconductor chip 3A mounted on the substrate 2A. The semiconductor chip 3A is bonded to the substrate 2A by an anisotropic conductive adhesive 4A. The illustrated adhesive 4A is made up of a thermosetting resin material 41A containing conductive substances 40A.
As illustrated, the semiconductor chip 3A is provided with connection terminals (conductive bumps) 30A, while the substrate 2A is provided with connection pads 20A. Each connection terminal 30A of the chip 3A is electrically connected to a corresponding one of the connection pads 20A on the substrate 2A via conductive substances 40A in the adhesive 4A. The semiconductor chip 3A is mechanically connected to the substrate 2A by the thermosetting resin material 41A in the adhesive 4A. The substrate 2A is formed with through-holes 21A corresponding in position to the connection pads 20A. Ball-like terminals 6A of solder are formed at the respective through-holes 6A to be electrically connected to the connection pads 20A.
As stated above, in the above conventional semiconductor device 1A, the mechanical bonding between the substrate 2A and the semiconductor chip 3A depends only on the thermosetting resin material 41A. Thus, disadvantageously, the semiconductor chip 3A may fail to be attached firmly to the substrate 2A. Consequently, the chip 3A may be accidentally detached from the substrate 2A rather easily upon application of an external force. Even if the chip 3A is only shifted in position relative to the substrate 2A, the device 1A may suffer from the short-circuiting of the wiring pattern.
The present invention has been proposed under the circumstances described above.
It is an object of the present invention to provide a semiconductor device in which a semiconductor chip is reliably attached to a base member.
Another object of the present invention is to provide a method of making such a semiconductor device.
According to a first aspect of the present invention, there is provided a semiconductor device which comprises a semiconductor chip, a base member for mounting the chip, anisotropic conductive adhesive arranged between the chip and the base member, and a package for enclosing the chip and the adhesive. The chip is secured to the base member by the adhesive and the package.
With such an arrangement, the chip is attached to the base member not only by the adhesive but also by the package. Thus, even if the bonding force of the adhesive is not strong enough, the package prevents the chip from being detached from the base member.
In a preferred embodiment, the package is held in direct contact with the base member.
The chip may be provided with at least one connection terminal, while the base member may be provided with at least one counterpart terminal held in facing relation to the connection terminal of the chip to be electrically connected thereto.
Preferably, the chip may have a bonding surface and side surfaces connected to the bonding surface. The adhesive may be held in contact with the bonding surface and a portion of each of the side surfaces.
Preferably, the base member may be an insulating substrate. The insulating substrate may be made of a glass-fiber-reinforced epoxy resin material or ceramic material for example.
Alternatively, the base member may comprise a film element having a bonding area reinforced for mounting the chip. It is possible to achieve the reinforcement of the bonding area by fixing a rigid plate, resin layer or wiring pattern to the bonding area.
In a preferred embodiment, the base member may comprise an additional semiconductor chip.
Preferably, the chip, the adhesive and the base member may be embedded in the package.
The conductive adhesive may comprise a thermosetting resin material containing conductive substances. This thermosetting resin material, before being caused to permanently set, is less rigid than a portion of the base member on which the chip is mounted.
Preferably, the package may be made of a thermosetting resin material which, prior to permanent setting, is less rigid than a portion of the base member on which the chip is mounted.
According to a second aspect of the present invention, there is provided a method of making a semiconductor device provided with a semiconductor chip, a base member and a protection package. The method may comprise the steps of: applying anisotropic conductive adhesive between the chip and the base member; provisionally attaching the chip to the base member by rendering the adhesive semi-solid; and forming the protection package to enclose the chip and the adhesive. The adhesive is rendered solid at the protection package forming step for securing the chip to the base member.
Preferably, the chip may be urged toward the base member by contraction of the protection package. The contraction may occur when the package solidifies and cools down.